Metal alkoxides and aryloxides are typically produced by reaction of the metal, or its halide with the respective alcohol, or aryl hydroxy compound or its salt, as illustrated in the following three reactions: ##STR2##
Typically, the metal is made by high temperature carbothermal (1200.degree. C.) or electrochemical reduction of some ore form of that metal such as SiO.sub.2 (Kirk-Othemer Encyclopedia of Chemical Technology, 3rd Ed.; WILEY-INTERSCIENCE PUBL., N.Y., New York (1979) Vol. 20, p. 750-880) or bauxite (see "The Production of Inorganic Materials", by De Jonge and Evans, MACMILLAN PUBL., 1990). The chloride is either made simultaneously, or sequentially by treating the metal with chlorine or HCl, as illustrated by: ##STR3##
In all of these processes, the pure metal or the halide are formed by high temperature processes which are energy inefficient and polluting. Only after the pure metal or halide are formed by such processes, is it possible to make the metal alkoxide or aryloxide. Thus, the common routes to alkoxides and aryloxides are multistep and polluting as well as energy and equipment intensive.
As an alternative, the direct chemical synthesis of alkoxides and aryloxides directly from metal oxides offers an opportunity to develop cheaper routes to these materials as well as novel materials. For example, the reaction of silicon with an alkali salt of catechol provides access to the hexaaryloxy dianionic silicon compound: ##STR4##
This type of reaction was first reported by Rosenheim et al in 1930 [A. Rosenheim, B. Raibmann, and G. Schendel, Z. Anorg, Chem. 196, 160 (1931)]. Laine et al have also described the preparation of penta- and hexaalkoxysilane anions and dianions. See "Silicon and Aluminum Complexes", R. M. Laine, K. A. Youngdahl and P. Nardi, U.S. Pat. No. 5,099,052, Mar. 24, 1992; and "Barium Tris(1,2ethandiolato)silicate, A Hexacoordinate Alkoxy Silane Synthesized From SiO.sub.2." M. L. Hoppe, R. M. Laine, J. Kampf, M. S. Gordon and L. W. Burggraf, Angew. Chem. (in press).
In all instances, these studies only teach the synthesis of anionic silicates with alkali or alkaline earth counterions. In no instance does the prior art teach a commercially viable synthesis of neutral siloxanes, aluminoxanes or polymeric species containing mixtures of neutral and anionic Si and/or Al centers from SiO.sub.2 or other siloxy compounds or the equivalent Al species.
U.S. Pat. No. 2,881,198 to D. Bailey and F. O'Connor taught that reacting silica with a catalytic amount of alkali metal under conditions that remove water by distillation or azeotrope (often under pressure) lead to the synthesis of monomeric, neutral alkoxy silanes. However, the disclosed reaction was extremely slow, requiring days to complete. Furthermore, the yields obtained were only 50-78%, as the alkali base used as the catalyst eventually reacted with the SiO.sub.2 to produce alkali silicate byproducts.
Frye appeared to teach that silicic acid will react with a large excess of triethanolamine to produce water and what was described as a "more or less nondescript silatrane material". Although the reaction which accompanied this disclosure incorrectly characterized the formula for silicic acid, the synthesis was predicated upon the use of TEA as the sole solvent. Also, the disclosure appears to be limited to relatively low molecular weight oligomeric species. See Frye et al., "Pentacoordinate Silicon Compounds. V. Novel Silatrane Compounds". Journal of Am. Chem. Soc. 93:25; Dec. 15, 1971 p. 6805-6811.
It is an object of this invention to provide neutral and mixed neutral/anionic polymetallooxanes of varying molecular weights so as to be classifiable as monomers, oligomers and polymers. It is a particular object of the present invention to provide such compounds having high molecular weights.
Another object of this invention is to provide a method of making the claimed compounds.
A further object is to provide a method of making neutral and mixed neutral/anionic polymetallooxanes containing alkoxy, aryloxy and alkoxylaryloxy ligands, using catalytic amounts of amines and polyamines to provide commercially viable rates of reaction.
A still further object of the present invention is to provide a method of making ceramic materials having controlled ceramic yield, stoichiometry, phase, microstructure, shape, and surface area, by utilizing the polymetallooxane compounds of the instant invention as ceramic precursors or preceramic materials.
Still another object of the present invention is to provide a method of making ceramic fibers and coatings.
Other objects of the invention include providing methods of making fibers, fine or monodispersed powders, coatings, porous articles such as ceramic foams, filters and membranes, and compression-molded and injection-molded articles using, inter alia, the preceramic polymers as provided herein.
Still other objects of the present invention include methods of using the polymetallooxane polymers of the invention as binders, as adhesives, in infiltration applications (as in wood preservation), and in matrix and composite materials.
Additional features of the invention will be set forth in the description which follows and will become apparent to those skilled in the art on examination of the following, or may be learned by practice of the invention.